Dark leaves means photosynthesis is happening. Clawed tips show photosynthates aren't moving fast enough after photosynthesis. Purple stems mean photosynthates are stuck in the phloem. The roots will be small because they lack phos and photosynthates.
It's phosphorus deficiency, but he has phos, you see it in the quality of the photosynthates. It's just not translocating. The only 2 things that could be holding up phosphorus are calcium or boron and I've never seen a boron deficiency. I see [soluble] calcium fix every grow I've consulated. The time saved on lst, vegging, plucking.. People have completely forgotten how uncontrollable the growth of this plant naturally is.. Months of veg time wasted, yields in the single percent of the genetic potential of the strain. Constantly manipulating plants because they don't branch correctly. I don't know if there's a conspiracy to make everyone waste their time growing a partial crop of premature mids or what, but literally every grow I look at has the same problem and could triple their yield by fixing calcium uptake. I promise you this blindness to calcium deficiency is strickly a cannabis issue. All the Cannabis charts wait until necrosis shows up and then panics to identify a symptom while ignoring the root cause. The plant tells you everything that's going to happen weeks prior.